[racket-dev] src-id in identifier-binding for same-module definitions

Does `identifier-binding` not give you the symbol that you need?

At Wed, 16 Jul 2014 23:32:46 -0400, Sam Tobin-Hochstadt wrote:
> Ok, I thought I had figured this out, but I was wrong.
> 
> Here's what I want to be able to do:
> 
>  - take an identifier in a fully-expanded source file
>  - translate that identifier to some symbol in a predictable way
>  - so that other references to that same (free-identifier=?)
> identifier get translated to the same symbol
> 
> It's pretty easy to do this in a single module -- just keep a
> free-id-table of all the identifiers mapping to gensyms. But I want to
> be able to do this across modules, and across invocations of this
> program. IOW, when I run my program on one source file, I'd like to
> get a symbol for a provided definition that's the same symbol I get
> when I run my program on a different source file containing a
> reference to that definition.
> 
> Clearly this is possible, since Racket manages, but is there a way
> that I can do it?
> 
> Sam
> 
> On Wed, Jul 16, 2014 at 7:55 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> > Yes, it can be ".2", etc. The numbers are generated as needed to create
> > distinct names --- deterministically for a given module compilation,
> > assuming that all macros used by expansion are deterministic.
> >
> > At Wed, 16 Jul 2014 07:36:50 -0400, Sam Tobin-Hochstadt wrote:
> >> Does that mean that I can/should just drop the .1 to get the defined name?
> >> Can it also be .2 etc?
> >>
> >> Sam
> >> On Jul 16, 2014 4:34 AM, "Matthew Flatt" <mflatt at cs.utah.edu> wrote:
> >>
> >> > That `posn1.1` is a unreadable symbol that stands for the symbol
> >> > `posn1` plus some marks that distinguish it.
> >> >
> >> > In other words, `posn1.1` bridges (in an ugly way) the symbol-based
> >> > world of module environments and the identifier-based world of syntax.
> >> > In the future, I hope to shift module environments to be
> >> > identifier-based to avoid these unreadable symbols.
> >> >
> >> > At Tue, 15 Jul 2014 09:10:26 -0400, Sam Tobin-Hochstadt wrote:
> >> > > If you take this program and fully-expand it in the macro stepper:
> >> > >
> >> > > #lang racket
> >> > > (struct posn (x y))
> >> > > (define p1 (posn 1 2))
> >> > >
> >> > > You see that the residual program has an application of the `posn1`
> >> > > function, which is the hidden constructor. And indeed, the
> >> > > fully-expanded program has a definition of `posn1`. However, if you
> >> > > click on the use of `posn1`, the macro stepper will tell you that it's
> >> > > defined in this module as `posn1.1`, and provided as `posn1.1` as
> >> > > well. If you write program to grovel through the fully-expanded
> >> > > syntax, you get these same results as the `src-id` and
> >> > > `nominal-src-id` from `identifier-binding`.
> >> > >
> >> > > Why is this? And is there a way to get from `posn1.1` to `posn1`
> >> > reliably?
> >> > >
> >> > > Sam
> >> >